Process for winding elastomeric fiber package

ABSTRACT

A winding process for an elastomeric fiber package using a contact roll that exerts variable pressure during the winding to create an elastomeric fiber package with a good package shape. The method including having a high initial force of the contact roll of less than 10 kg, reducing the force to about 25-60% of the initial force during the first 30% of winding time, then holding the force substantially constant until the final 30% of the winding time when the force is reduced to about a final force of 10-35% of the initial force. Wherein the final force is no less than about 1 kg and the package size is at least 4 kg.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a winding process for an elastomericfiber package and, more particularly, to a process for winding a packageutilizing a contact roll exerting variable pressure during the winding.

2. Description of Background Art

Products based on elastomeric fibers have been used in many areas suchas industrial materials, clothing, and disposable personal care products(for example diapers). The elastomeric fibers have been woven and knitinto fabrics, stitch-bonded into nonwovens, and directly adhered ontosheet materials such as nonwovens and films. The elastomeric fiber isordinarily provided wound onto tubecores. The woundfiber and associatedtubecore are referred to as a “package”. In use, the elastomeric fiberis unwound from the package sequentially or in parallel, eitherpassively (for example, by “over-end take-off”) or actively (for exampleby “rolling take-off”), and fed to a downstream process.

However, there have been problems in that elastomeric fiber packageshave heretofore sometimes had poor package shape. Such packages havebeen wound with rising force of the contact roll on the tubecore andpackage. This poor package shape can cause the elastomeric fiber toslough off the package readily (for example as a result of rubbingagainst shipping materials or other elastomeric fiber packages) so thatthe unwinding elastomeric fiber becomes entangled with the sloughed-offelastomeric fiber, leading to breaks in the fiber. Such breaks alsooccur as a direct result of the rubbing. As a result, the economics ofunwinding fibers from such packages were poor, and an improved processfor winding elastomeric fiber packages is needed.

SUMMARY OF THE INVENTION

The process for winding an elastomeric fiber producing an inflectedforce profile, comprises the steps of:

(A) rotating a tubecore in contact with a contact roll;

(B) winding the fiber onto the tubecore so that the contact roll exertsan initial force against the fiber on the tubecore and a package beginsto be formed;

(C) gradually reducing the force a first time during the first 30% ofwinding time to approximately 25-60% of the initial force;

(D) holding the force substantially constant until the final 30% ofwinding time; and

(E) reducing the force a second time to no less than approximately 10%of the initial force.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic side view illustrating an elastomeric fiberpackage obtained by the process of the invention.

FIG. 2 is a plot of the force that the contact roll exerts against thetubecore and package vs package diameter from the beginning of windingto the end of winding in the process of the present invention. This isan example of an inflected force profile.

FIG. 3 shows a cross-section of an elastomeric fiber package made byconventional winding.

FIG. 4 illustrates an example of an uninflected force profile as used ina conventional winding process.

FIG. 5 schematically illustrates an example of a means that can be usedin the present process to vary the force that the contact roll exertsagainst the elastomeric fiber package.

DETAILED DESCRIPTION OF THE INVENTION

It has now been found that an elastomeric fiber package, especially alarge package which has good unwinding characteristics and excellentpackage shape, can be made by winding the package with an inflectedforce profile.

“Elastomeric fiber” means a filament which has a break elongation inexcess of 100% independent of any crimp and which when stretched andreleased, retracts quickly and forcibly-to substantially its originallength. Such fibers include rubber fiber, spandex or elastane,polyetherester fiber, polyetheramide fiber, certain polypropylenes, andelastoester. “Spandex” and. “elastane” mean a manufactured fiber inwhich the fiber-forming substance is a long chain synthetic elastomercomprised of at least 85% by weight of a segmented polyurethane.“Inflected force profile” means a plot of the package diameter vs theforce of the contact roll against the tubecore and winding package, theplot having a change of curvature, with respect to a fixed line, fromconcave to convex, or conversely, depending on the point from which theplot is viewed.

Synthetic elastomeric fibers such as elastane, polyetheramide fibers,and polyetherester fibers can be prepared from polymeric glycols;copolymeric glycols can also be used. In the case of elastane, thepolymeric glycol can be a (co)polyether glycol, (co)polyester glycol,and/or (co)polycarbonate glycol. The polymeric glycol is typicallyreacted with a diisocyanate and at least one diamine, alkanolamine,and/or diol to form the polymer. In the case of polyetheresters, apolyether glycol can be reacted with a diacid and at least onelow-molecular weight diol to form the polymer. Polyether diamines,diacids, and low molecular weight diamines can be used to makepolyetheramides. Monofunctional chain terminators such as alcohols andamines can be used to control the molecular weight of the polymers.

Depending on the type of polymer to be made, solution- ormelt-polymerization can be used. Correspondingly, dry-, wet-, ormelt-spinning can be used to prepare the fiber, depending on the type ofpolymer. Additives and stabilizers can be added to the fiber, providedthey do not adversely affect the process of the invention.

After the fiber has been spun, it is typically reciprocated transverselyto the direction of its travel by a traverse means and wound up on atubecore. The tubecore is customarily mounted on a spindle assembly, andthe fiber is wound onto the tubecore with the aid of a contact roll. Thespindle assembly can be driven and the contact roll can be undriven(freely rotating). Alternatively, the spindle assembly can be undriven,and the contact roll can be driven, thus providing the rotational driveneeded to rotate the spindle assembly.

In the process of the present invention, the force exerted by thecontact roll on the tube core (and after winding begins, on the growingpackage) is reduced during winding according to a specific profile. Theforce reductions are described herein by reference to the force used atthe beginning of winding (the “initial force”). The maximum initialforce can be 10 Kg, and the minimum force can be 1 Kg. During the first30%, preferably 10%, of winding time, the force is gradually reduced afirst time, to about 25-60% of the initial force. The contact roll forceis then held substantially constant until the final 30%, preferablyabout 20%, of the winding time at which point the force is reduced asecond time to no less than about 10%, preferably about 10-35%, of theinitial force. Winding time corresponds approximately to packagediameter, and plotting the contact roll force against the diameter ofthe winding package gives an inflected force profile as illustrated inFIG. 2.

The method of this invention provides an elastomeric fiber package whichhas a substantially uniform wound width, thereby providing excellentunwinding and shape retention properties. That is, the present inventionproduces a package as illustrated in FIG. 1, which has a smalldifference δ_(ω) between the maximum value δ_(max) and the minimum valueδ_(min) of the wound package width. A small δ_(ω) indicates sidewallsthat are desirably substantially flat and perpendicular to the axis ofthe tubecore; such packages have good unwinding characteristics.

The process of the invention is especially useful for elastomeric fiberpackages weighing 3 kg or more and even exceeding 4 kg.

Any suitable method can be used in this invention as a means to controland vary the force that the contact roll exerts against the package. Forexample, an apparatus as illustrated in FIG. 5 can be used in whichcompressed air cylinder 5 operates on signals from a control device (notshown) to adjust the weight of arm 4 that supports contact roll 3 whichrotates in contact with tubecore and package 1 as elastomeric fiber 2 iswound up. Thus when the cylinder is extended, the contact roll force isreduced, and when it is contracted, the force is increased. A hydrauliccylinder can be used in place of the air cylinder. Other geometries canalso be used to obtain the inflected force profile of the invention.

EXAMPLE 1

A 560 denier (622 dtex) Lycra® spandex (Type 127; a registered trademarkof E. I. du Pont de Nemours and Company) was dry-spun by conventionalmeans and wound up on a 175-mm long tubecore to reach a wound packageweight of 4.5 kg. No finish was applied to the fiber. The force that thecontact roll exerted against the package during winding followed theinflected force profile shown in FIG. 2, in which package diameter (inmm) is plotted on the abscissa and the force that the contact rollexerts against the package (in Kg) is plotted on the ordinate. As shownin FIG. 2, the total winding diameter was about 282 mm. The beginning ofwinding, during which the contact roll force was reduced a first time,was about 9 mm (5% of the total diameter and about 5% of the totalwinding time), and the end of winding during which the force was reduceda second time was about 46 mm (24% of the total diameter and about 24%of the total winding time). The force declined from about 5.7 Kg at thebeginning of winding to about 2.9 Kg during the middle of winding, or toabout 50% of the initial force. The contact roll force was heldsubstantially constant until the end of winding, at which point it wasreduced further to about 31% of the initial force, in other words toabout 1.8 Kg. As shown in Table 1, the difference in wound width wassmall and the product had excellent sidewall shape and unwindingcharacteristics.

Comparative Example 1

Elastomeric fiber was spun and wound up exactly as in Example 1 exceptthat the force that the contact roll exerted against the package wasincreased as during conventional winding and as shown in FIG. 4. Asreported in Table 1, the resulting package had a wound width greaterthan that of the package of Example 1, showed inferior unwindingcharacteristics, and had an S-shape (substantial bulge) in the sidewallas illustrated in FIG. 3.

TABLE 1 Example 1 Comp. Example 1 The curve shape of Inflected forceLinear, as in the force that profile, as in FIG. 4 contact roll exertsFIG. 2 against package Difference in wound 16 30 width δ_(w) (mm)Sidewall shape Gentle curve S-shaped, with large bulge Unwinding GoodPoor characteristics

What is claimed is:
 1. A process for winding an elastomeric fiber (2),comprising the steps of: (A) rotating a tubecore in contact with a roll(3); (B) winding the fiber onto the tubecore so that the contact rollexerts an initial force no greater than about 10 kg against the fiber onthe tubecore and a package (1) begins to be formed; (C) reducing theforce a first time to about 25-60% of the initial force during the first30% of winding time; (D) holding the force substantially constant untilthe final 30% of winding time; and (E) reducing the force a second timeto about a final force that is 10-35 k of the initial force, wherein thefinal force is no less than about 1 kg and the package size is at least4 kg.
 2. The process of claim 1 wherein the force is reduced a firsttime during about the first 10% of winding time and the force is reduceda second time during about the final 20% of winding time.